Mr Al Hawaj said the project includes construction of a new treatment plant next to the current one and a collection for wastewater streams 23m underground.
A main pumping station 28m underground will receive wastewater flows from the collection room.
Mr Al Hawaj highlighted the strategic importance of the project, which will double the plant's capacity.
It aims to absorb the increased wastewater flow into the station as a result of urban development and population increase.
"Increasing the plant's capacity from 200,000 cubic meters to 400,000 cubic metres per day and raising the performace of the Tubli plant for production of treated water will contribute to improving the environmental situation and wildlife in the region and Tubli Bay", said Mr Al Hawaj.
"In particular, increase in the production of treated water used for irrigation and agricultural beautification will positively affect the indicators of sustainable development in the kingdom, as the volume of flows that reach the centre now is 330,000 cubic metres per day."
The scheme will also include three treatment units - a sand filters unit, ozone gas purification unit and chlorine purification unit - a balance basin and sludge incineration unit. Work will soon begin on construction of a laboratory, workshops and an administration unit, he said.
The GDN reported early this year that the fourth and final phase of the project at the Tubli Wastewater Treatment Plant has already started - and will include multiple treatment of sewage water for agriculture use, along with incinerating sludge and ensuring the remaining water disposed at the protected Tubli Bay is harmless and odourless.
The fourth and final phase is expected to be completed by January 2022.
